Remote unit for providing spatial processing

ABSTRACT

Methods and apparatus implementing spatial processing in a remote unit. In general, in one aspect, a remote unit in accordance with the invention includes a spatial processing unit to process signals received by a plurality of antennas.

RELATIONSHIP TO OTHER APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/853,992 filed Sep. 12, 2007 now U.S. Pat. No. 7,702,298 toinventors Barratt et al., entitled “METHOD AND APPARATUS TO PROVIDEMULTIPLE-MODE SPATIAL PROCESSING IN A RADIO RECEIVER” which is itself acontinuation of U.S. patent application Ser. No. 10/265,896 filed Oct.7, 2002 to inventors Barratt et al., entitled “METHOD AND APPARATUS TOPROVIDE MULTIPLE-MODE SPATIAL PROCESSING TO A TERMINAL UNIT” and whichissued on Oct. 2, 2007 as U.S. Pat. No. 7,277,679. Such patentapplications are hereby incorporated herein by reference.

U.S. patent application Ser. No. 10/265,896 was a continuation-in-partof U.S. patent application Ser. No. 09/967,863 filed 28 Sep. 2001 toinventors Barratt et al., titled A METHOD AND APPARATUS FOR PROVIDINGSPATIAL PROCESSING IN A REMOTE UNIT, and which issued Nov. 15, 2005 asU.S. Pat. No. 6,965,788. Such patent application is hereby incorporatedherein by reference.

The discussion of FIGS. 1, 1A, 1B, 2A, 2B and 3-10 in the DetailedDescription below corresponds to the discussion in U.S. patentapplication Ser. No. 09/967,863 of respective FIGS. 1, 1A, 1B, 2A, 2Band 3-10.

U.S. patent application Ser. No. 10/265,896 also claimed priority toboth U.S. provisional patent application Ser. No. 60/386,183 filed 31Dec. 2001 to inventors Barratt et al., titled METHOD AND APPARATUS FORPROVIDING A MULTIPLE-MODE SPATIAL PROCESSING TERMINAL UNIT, and to U.S.provisional patent application Ser. No. 60/386,184 filed 31 Dec. 2001 toinventors Barratt et al., titled METHOD AND APPARATUS FOR PROVIDING AMULTIPLE-MODE TERMINAL UNIT. Such provisional patent applications arehereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to wireless communication systems.

Generally, wireless communication systems include multiple base stationsin different geographic areas. Each base station provides services forremote units within the base station's geographic area.

Base stations and remote units are distinguishable. Generally, remoteunits include termination devices in a wireless communication system. Incontrast, a base station is not a termination device. Rather, a basestation usually relays traffic between or among termination devices.Another distinguishing feature between a base station and a remote unitis that a base station can simultaneously communicate with multipleremote units while a remote unit usually communicates with only one basestation (except in certain situations such as handover).

Remote units include cellular phones. Although cellular telephones wereinitially limited to bulky systems installed in automobiles, they havedeveloped into more compact, portable, and multi-functional voice anddata-capable communication devices. Remote units also include othertypes of stationary and mobile wireless communication devices, any ofwhich may provide wireless communication and processing of anycombination of voice and data signals using any combination of analogand digital techniques. Such devices include, but are not limited to,cellular-type voice and data handsets, wireless modems (e.g., PCMCIA)for portable or fixed computing systems, wireless personal digitalassistants, wireless two-way pagers, and wireless Web pads.

Remote units are operable in various types of wireless communicationsystem architectures and protocols, including but not limited tocellular systems (e.g., AMPS, CDMA, GSM, and PHS), wireless local areanetwork (“WLAN”), microwave point-to-multipoint systems, peer-to-peerwireless communication systems, and so forth. Remote units typicallyprovide various types of voice and/or data communication functionalities(also referred to as requested services) that may be enabled byhardware, software, or any combination thereof.

To facilitate processing and communication of voice and data signals,remote units may include a display, a numeric or alphanumeric keypad,pointing device, speaker and/or microphone, digital video/photo camera,data storage, Web browsing capability, instant/text messagingcapability, and a graphical user interface.

Some remote units, such as cellular phones, are mobile. Usually, mobileremote units are designed to be relatively small in size in order tofacilitate portability. Such remote units typically have a relativelysmall antenna and power source, such as a small rechargeable batteryhaving a limited power capacity. As a result, remote units may be moresusceptible to interference and other types of transmission (Tx) and/orreception (Rx) performance degradation and may suffer from limited powerresources. Generally, the performance level of a remote unit indicateshow well the remote unit is communicating with other devices. In mostwireless communication systems, performance is measured by someindication of error in signal processing. Examples of such indicationsof error include but not limited to bit error rate (“BER”) and frameerror rate (“FER”). Other indicia of performance include but not limitedto metrics of signal quality, such as a signal to noise ratio (“SNR”) ora signal to interference and noise ratio (“SINR”), and receive signalstrength indication (“RSSI”).

SUMMARY OF THE INVENTION

The present invention provides methods and apparatus, including computerprogram products, for spatial processing in a remote unit.

In general, in one aspect, the present invention provides a remote unitthat includes a spatial processing unit to couple to a plurality ofantennas.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a remote unit in accordance with the invention.

FIG. 1A shows a remote unit that is a mobile phone.

FIG. 1B shows a more detailed view of the spatial processing unit ofFIG. 1.

FIG. 2A shows a receive path of the remote unit of FIG. 1.

FIG. 2B shows a transmit path of the remote unit of FIG. 1.

FIG. 3 shows a flow diagram of a method for conserving power in a remoteunit, in accordance with one embodiment of the invention.

FIG. 4 shows a flow diagram of a method for conserving power in a remoteunit, in accordance with one embodiment of the invention.

FIG. 5 shows a flow diagram of a method for conserving power in a remoteunit, in accordance with one embodiment of the invention.

FIG. 6 shows a flow diagram of a method for determining, during spatialprocessing operations, when to enable an additional antenna and when todisable an enabled antenna, in accordance with one embodiment of theinvention.

FIG. 7 shows a flow diagram of a method for determining, during spatialprocessing operations, when to enable an additional antenna and when todisable an enabled antenna, in accordance with one embodiment of theinvention.

FIG. 8 shows a flow diagram of a method for adjusting feedback to allowa remote unit to benefit from spatial processing gains, in accordancewith one embodiment of the invention.

FIG. 9 shows a flow diagram of a method for adjusting feedback to allowa remote unit to benefit from spatial processing gains, in accordancewith one embodiment of the invention.

FIG. 10 shows a flow diagram of a method for adjusting feedback to allowa remote unit to benefit from spatial processing gains, in accordancewith one embodiment of the invention.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Overview

A remote unit in accordance with the invention includes an antennaarray, corresponding receive paths, and a spatial processing unit. Thespatial processing unit advantageously improves the performance of theremote unit. For example, during downlink, the onboard spatialprocessing unit improves received signal quality.

In accordance with one inventive aspect, the remote unit furtherincludes a power conservation unit for determining when the remote unitshould perform spatial processing. For instance, in one embodiment, thepower conservation unit determines the number of antennas that should beused and/or the number of receive paths to be enabled during spatialprocessing operations, in each case considering factors such asperformance level and power conservation. The power conservation unitadvantageously improves power efficiency of the remote unit.

For example, in one embodiment of the invention, during spatialprocessing operations and when a performance level of the remote unitsatisfies certain criteria, the remote unit disables one or more receivepaths, thereby conserving power and hence battery life. When theperformance level satisfies other criteria, the remote unit enables oneor more additional receive paths. Criteria for disabling an enabledreceive path include having a performance level that exceeds apredetermined quality of service. Criteria for enabling an additionalreceive path include having a performance level that is below thepredetermined quality of service. By determining performance level andadjusting the number of receive paths that are enabled, the remote unitis power efficient during spatial processing operations and,consequently, does not impractically drain its battery.

In accordance with another inventive aspect, the remote unit alsoincludes a feedback adjustment unit for adjusting feedback to a basestation that may adjust operating parameters, such as and not limited todata transfer rate, channel assignment, handover, and/or transmit power,in response to feedback from remote units. In one embodiment, feedbackadjustment depends on whether the base station's response to a reportedperformance gain by the remote unit adversely or beneficially affectsthe remote unit.

Specifically, when the remote unit is communicating with a base stationwhose response to a reported performance gain adversely affects theremote unit, the feedback adjustment unit adjusts feedback so that thebase station does not adjust operating parameters in response to anyperformance gained from the spatial processing operations and thereforedegrade the remote unit's performance. Consequently, the remote unit isadvantageously able to benefit from any resultant performance gain. Inone embodiment, the spatial processing operations can be enabled by auser, by a base station or other device, or automatically by the remoteunit itself to increase the remote unit's performance level, forexample, when transmitting or receiving signals of high interest, suchas signals for an important fax or an important conversation. Byincreasing the remote unit's performance level and having the downlinkbase station maintain operating parameters, the probability of droppingan important communication can be reduced.

On the other hand, when the remote unit is communicating with a basestation whose response to a reported performance gain benefits theremote unit, the feedback adjustment unit adjusts feedback so that thebase station does adjust operating parameters in response to anyperformance gained from the spatial processing operations and thereforeenhance the remote unit's performance. Consequently, the remote unit isadvantageously able to benefit from the performance gained from spatialprocessing.

One Embodiment of a Remote Unit in Accordance with the Invention

As shown in FIG. 1, a remote unit 100 in accordance with the inventionincludes an antenna array having antennas 102 a and 102 b, a transmitpath 103, receive paths 104 a and 104 b, a baseband processor 105, apower source 107 (such as a small rechargeable battery), and a duplexer109. The receives paths 104 a and 104 b share a local IF oscillator 111and a local RF oscillator 113. Each of the transmit path 103 and receivepaths 104 a and 104 b includes signal processing devices that preparesignals for processing in baseband processor 105 or for transmission outantenna 102 a. The paths are further described below with reference toFIGS. 2A and 2B. The baseband processor 105 includes a transmitmodulator 115 that produces signals to be forwarded to transmit path103, duplexer 109, and antenna 102 a. Although the remote unit 100 shownincludes only two antennas, three or more antennas and associatedreceive paths can be provided.

FIG. 1A shows a remote unit that is a mobile phone handset 117, inaccordance with one embodiment of the invention. The mobile phonehandset 117 includes a graphical user interface such as display 119 forinteraction with a user. The mobile phone handset 117 also includes analpha numeric keypad 121 for receiving input. The keypad 121 includes abutton 123 for enabling and disabling spatial processing. Alternatively,the display 119 provides a menu or an icon for enabling and disablingspatial processing. The mobile phone includes antenna 102 a and 102 b,the latter of which is not depicted for clarity. In one embodiment, theantenna 102 b is internal to the mobile phone handset 117. In otherembodiments, the antenna 102 b can be external and have similar ordifferent characteristics as antenna 102 a. A remote unit in accordancewith the present invention may include two or more antennas, any one orcombination of which may be internal and/or external. FIG. 1A shows butone embodiment of a remote unit, various other embodiments ofcellular-type voice and data handsets as well as other embodiments of aremote unit are possible. Other embodiments of a remote unit include butare not limited to wireless modems (e.g., PCMCIA) for portable or fixedcomputing systems, wireless personal digital assistants, wirelesstwo-way pagers, and wireless Web pads.

Spatial Processing

Baseband processor 105 (FIG. 1) also includes spatial processing unit106 that processes signals received through antennas 102 a and 102 b.Generally, spatial processing unit 106 takes advantage of the physicalseparation between the antennas 102 a and 102 b, which separationprovides uncorrelated diversity branches. Diversity branches can beprovided through physical diversity, including not but not limited tohaving physically separate antennas, using antennas of different shapesor materials, or any combination thereof. Alternatively, the remote unit100 employs other techniques for constructing diversity branches of areceived signal. These techniques include but are not limited to anglediversity (also known as direction diversity) and polarizationdiversity. Angle diversity uses multiple directional antennas. Eachantenna responds independently to a radio wave propagating at a certainangle and thus receives a diversity branch of the wave that is notcorrelated with the other branches received at the other antennas. Inpolarization diversity, two antennas are situated such that they havedifferent polarization to provide two diversity branches. Any one orcombination of diversity techniques, such as those described above, maybe employed in various embodiments of the invention.

Spatial processing unit 106 combines or selects the diversity branchesto improve performance of the remote unit 100. Methods for combining orselecting diversity branches include but are not limited tomaximal-ratio combining, equal-gain combining, and selection, any ofwhich can be used by the spatial processing unit 106.

FIG. 1B shows one embodiment of spatial processing unit 106. A channelestimation processor 120 calculates a channel estimate for each of thereceived antenna signals by convolving the received signal with a knownpilot or training sequence. For example, in a GSM system, the middleportion of each burst contains a known 26 bit training sequence.Similarly in CDMA, a known pilot signal is contained in the receivedsignal. The channel estimate contains information about the relativepower, timing, and phase of the multipath copies of a given signal andis calculated separately for each antenna. Typically, this channelestimate is updated frequently because the channel changes as the userand environment move. In one embodiment, the channel estimate is updatedat the frame or burst rate in the system. Alternatively, the channelestimate is updated at a regular rate, for example every ten (10)milliseconds.

In maximal gain combining, spatial processing unit 100 acts to combinethe signal from each of the antennas while first weighting ormultiplying the signal with a factor that is proportional to the powerof the signal as determined by the channel estimate. Weighting andcombining is executed in a spatial combiner 122. The weighting factorcan be complex and include a phase rotation that rotates the phase ofeach of the antenna signals so that the signals are in phase when theyare combined. Maximal gain combining serves to maximize the signal tonoise ratio of the combined signal. Embodiments of the invention are notrestricted to using the described maximum gain combining technique. Anyone or combination of combining or selection techniques can be used tocombine or select diversity branches.

In a specific example, the channel estimate for a two antenna remotemight be:

Antenna 1: 0.8 at angle 50 degrees

Antenna 2: 0.5 at angle −85 degrees.

Or more concisely ChanEst=(0.51+0.61 j, 0.04−0.49 j)

The “maximal gain combining weight” for this example would then be

W1=0.8 at −50 degrees

W2=0.5 at −85 degrees

If S1 is the received signal from antenna 1, and S2 is the receivedsignal from antenna 2, the combined signal SC computed by the spatialcombiner would then be: SC=W1*S1+W2*S2. This combined signal, SC, wouldthen be passed to the conventional receiver processing for the systemfor demodulation.

In one embodiment, one type of spatial processing technique such asMinimum Mean Squared Error (“MMSE”), is used to not only improve thesignal to noise ratio of the combined signal, but also to improve thecarrier to interference ratio of the combined signal in the presence ofa strong interfering signal, such as a signal from a neighboring basestation. In this method, a covariance matrix, Rzz, is formed by a Rzzaccumulation processor 124 from the received signals in addition to thechannel estimate. For a two-antenna remote unit,Rzz=S1*S1′, S1*S2′S2*S1′, S2*S2′

The inverse of the covariance matrix is computed by a Rzz inversionprocessor 126. The weight vector is then calculated by a spatial weightprocessor 128. The spatial weight processor 128 then multiplies thechannel estimate by the inverse of the covariance matrix.(W1,W2)=inv(Rzz)*ChanEst

The combined signal is then formed by the spatial combiner 122:SC=W1*S1+W2*S2

This weight vector is used by the spatial combiner 122 to produce acombined signal that has a maximum carrier to interference ratio giventhe two antenna signals. In the current embodiment, the covariancematrix and the weight vector are updated every time the channel estimateis updated, namely, at the frame or burst rate in the system orotherwise every 10 msecs. The spatial weight processor 128 also producesa signal quality improvement estimate, based on the quality of the knowntraining or pilot data in the received signals, that is supplied to thefeedback adjustment unit 118.

The described mathematical techniques can be employed to formsubstantially the same MMSE solution without requiring the inversion ofRzz. The invention may employ a combination of various spatialprocessing techniques, including but not limited to MMSE. Some spatialprocessing techniques are described in U.S. application Ser. No.09/727,261 filed on Nov. 30, 2000, which is hereby incorporated byreference in its entirety, and also in U.S. Pat. No. 6,275,453 issued onAug. 14, 2001, which is also hereby incorporated by reference in itsentirety.

Referring again to FIG. 1, the remote unit 100 optionally includes auser input (not shown) for manually enabling and disabling spatialprocessing. In one embodiment, the input may be a mechanical button suchas mechanical button 123 shown in FIG. 1A. Actuation of the mechanicalbutton causes the switch 114 c to open, cutting power to the spatialprocessing unit. Alternatively, the user input is an on-screen button.The user input can also be a voice activated command that causes theswitch 114 c to open. Furthermore, instead of or in combination withdisabling power to the spatial processing unit and/or a receive path,the user input can send signals to the spatial processing unit 106directing the spatial processing unit 106 to stop or start spatialprocessing.

Power Conservation

Baseband processor 105 also includes a power conservation unit 108 thatincludes power conservation logic for determining a number of receivepaths to be enabled for spatial processing operations, consideringfactors such as performance level and power consumption. The number ofreceive paths enabled can be the number of receive paths that providethe best performance gain to power consumption ratio. The powerconservation logic includes logic for determining, during spatialprocessing operations, when to enable and when to disable a receivepath.

The power conservation unit 108 receives as input determined performancelevels. The determined performance level can include one or anycombination of various indications of performance. Such indications canbe based on, for example, measurement, estimation, averaging, etc., ofperformance. In one embodiment, the measured performance input 112includes but is not limited to one or a combination of the following:measures of error in signal processing, such as FER and BER, andmeasures of signal quality, such as SINR, SNR, and RSSI.

In one embodiment, the power conservation unit 108 enables at least thenumber of receive paths to satisfy a predetermined quality of servicesuch as that imposed by a particular wireless system's operatingparameters, system architecture, or standard. The operation of the powerconservation unit 108 and the power conservation logic is describedbelow with reference to FIGS. 3-7.

As shown in FIG. 1, baseband processor 105 further includes a controller110 that enables and disables receive paths 104 a and 104 b based oninput provided by the power conservation unit 108. Controller 110receives input from the power conservation unit 108, including signalsinstructing the controller 110 to enable an additional receive path andsignals instructing the controller 110 to disable an enabled receivepath. In response to these inputs, controller 110 outputs power controlsignals to open and shut switches 114 a and 114 b in the power lines 116a and 116 b to receive paths 104 a and 104 b, respectively. Duringspatial processing operations, power conservation unit 108 andcontroller 110 operate in conjunction to dynamically and selectivelyadjust, in response to changes in the determined performance level, thenumber of receive paths that are enabled, and/or the complexity ofspatial processing technique employed, or if spatial processing isemployed at all.

Optionally, in addition to determining the number of receive paths to beenabled during spatial processing operations, the power conservationunit also determines when the remote unit 100 should perform spatialprocessing, considering similar factors involved in determining thenumber of receive paths to be enabled during spatial processingoperations. When the power conservation unit 108 has determined that theremote unit 100 should not perform spatial processing, powerconservation unit 108 sends instructions to the controller 110 to openswitch 114 c in power supply line 116 c, reducing power delivery to orprocessing speed/complexity of the spatial processing unit 106.Alternatively, instead of disabling or reducing power to the spatialprocessing unit 106, the power conservation unit sends instructions tothe spatial processing unit 106 to cease spatial processing. (Theelectrical connection for communication between the power conservationunit and the spatial processing unit is not shown.)

Feedback Adjustment

In one embodiment of the invention, the spatial processing unit 106includes a feedback adjustment unit 118 for adjusting feedback whencommunicating with a base station. Although the feedback adjustment unit118 shown is part of the spatial processing unit 106, such aconfiguration is not required. As discussed, this inventive feature maybe employed where a base station uses feedback from remote units toadjust operating parameters such as data transfer rate, downlink powercontrol, channel assignment, or others in response to such feedback. Inone embodiment, the feedback adjustment depends on whether the basesstation's response to a reported spatial processing gain by the remoteunit is adverse or beneficial to the remote unit.

When the base station's response adversely affects the remote unit, thefeedback adjustment unit, in one embodiment, adjusts feedback so thatthe base station does not adjust operating parameters. For example, abase station can adjust its transmit power in response to reports ofperformance from the remote units operating in the base station'sgeographic area. These reports (i.e., the feedback) indicate the remoteunit's current performance level. When a remote unit reports a lowperformance level, the base station typically increases its transmitpower to maintain a predetermined quality of service. When a remote unitreports a high performance level, the base station typically lowers itstransmit power while maintaining the predetermined quality of service.Accordingly, any gain attributable to spatial processing in a remoteunit as proposed herein may not be realized by the remote unit in neteffect.

Feedback adjustment unit 118 solves this problem by adjusting feedbackso that a base station that includes a feedback mechanism will not “see”the performance gain realized through the use of spatial processing in aremote unit. The feedback adjustment unit 118 includes feedbackadjustment logic for determining a performance level for non-spatialprocessing operations and logic for adjusting, in view of the determinedperformance level, the feedback the remote unit 100 transmits to a basestation. In one embodiment, the feedback adjustment unit 118 usesreceived measured input 112 to determine a non-spatial processingperformance level of the remote unit 100.

As discussed, the determined performance level can include one or anycombination of various indications of performance. Such indications canbe based on, for example, measurement, estimation, averaging, etc., ofperformance. In one embodiment, the measured performance input 112includes but is not limited to one or a combination of the following:measures of error in signal processing, such as FER and BER, andmeasures of signal quality, such as SINR, SNR, and RSSI. In anotherembodiment, measured performance input 112 indicates the actualperformance level of the remote unit 100. For example, during spatialprocessing operations, measured performance input 112 indicates theactual performance level accounting for any gain from spatialprocessing. In contrast, the estimated performance level provided as anoutput by feedback adjustment unit 118 indicates either actualperformance level or some other adjusted performance level. For example,the estimated performance level can be adjusted to indicate anon-spatial processing performance level even when the remote unit 100is operating in a spatial processing mode. Consequently, the gain fromspatial processing unit 106 is not apparent to a base stationcommunicating with remote unit 100. As such, the base station does notadjust its operating parameters, e.g., lower transmit power or increasedata transfer rate, and the remote unit benefits from the improvedperformance.

There are many ways to estimate a non-spatial processing performancelevel during spatial processing operations. For example, the remote unit100 can calculate an average performance gain from spatial processing,measure the current performance level during spatial processingoperations, and subtract the calculated gain from the measuredperformance level to derive an estimated performance level fornon-spatial processing operations. This implementation and others arefurther described below with reference to FIGS. 8-10.

When the base station's response to a reported spatial processing gainbenefits the remote unit, the feedback adjustment unit, in oneembodiment, adjusts feedback so that the base station does adjustoperating parameters. For example, when the remote unit is communicatingwith a base station that is using feedback from the remote unit fordetermining the maximum data rate sustainable to the remote unit, thefeedback adjustment unit provides feedback indicating that the remoteunit is taking full advantage of the spatial processing gain so that thebase station correctly concludes that a high data rate can be maintainedto the remote unit and, furthermore, maintains such a data rate.Consequently, the remote unit is advantageously able to benefit from theperformance gained from spatial processing.

A Receive Path

FIG. 2A shows the receive path 104 a and the devices therein. As shown,the receive path 104 a includes a low noise amplifier 202, mixers 204and 210, a surface acoustic wave filter 206, an amplifier 208, a filter212, and an analog to digital converter 214. The receive path 104 ashares external local oscillators with receive path 104 b (not shown inFIG. 2A). In operation, the antenna 102 a receives a signal which theduplexer 109 routes to the receive path 104 a. The devices in thereceive path 104 a prepare the signal for processing in a basebandprocessor, such as baseband processor 105. Receive path 104 b is similarto receive path 104 a.

A Transmit Path

FIG. 2B shows the transmit path 103 and the devices therein. As shown,the transmit path 103 includes a digital to analog converter 216, afilter 218, mixers 220 and 226, an amplifier 222, a surface acousticwave filter 224, and a power amplifier 228. Unlike the receive paths 104a and 104 b which use external local oscillators, the transmit path 103has internal local oscillators. In other embodiments, the receive andtransmit paths can share local oscillators. In operation, the transmitmodulator 115 (FIG. 1) sends a signal to be transmitted to the transmitpath 103 which prepares the signal for transmission. The duplexer 109(FIG. 1) routes the signal to be transmitted to the antenna 102 a. Thereceive and transmit paths described are illustrative and, accordingly,other implementations of transmit and receive paths can be used, forexample, quadratures or direct conversion architectures.

Methods for Conserving Power

FIG. 3 shows a flow diagram of a method for conserving power in aspatial processing remote unit, such as remote unit 100, in accordancewith one embodiment of the invention. As shown, the remote unitperiodically enables all receive paths (step 302). While all receivepaths are enabled, the remote unit determines a current performancelevel (step 304) and compares the current level to that measuredimmediately before all the receive paths were enabled. This comparisonyields a performance gain. The remote unit evaluates whether the gainwarrants the additional power consumed by the additional antennas andantenna paths (step 306). The evaluation is based on the performancegained versus the power consumed by enabling additional receive paths.The remote unit then uses the evaluation to selectively disable receivepaths (step 308).

FIG. 4 shows a flow diagram of a method for conserving power in aspatial processing remote unit, such as remote unit 100, in accordancewith one embodiment of the invention. The remote unit determines thetype of service being requested (step 402). As discussed, the type ofservice includes voice services and data services. Voice servicesinvolve voice communications directly or indirectly and between or amongindividuals and typically include establishing and maintaining callsthrough a PSTN or a packet based network. Data services involve thetransfer of data, digital or analog, and include sending and receivingfacsimiles and searching and retrieving of data from information storessuch as the Internet. Requested services typically have different datatransfer rates with data services usually requiring faster data transferrates than do voice services.

In one embodiment, the remote unit enables a predetermined number ofreceive paths corresponding to the type of service requested (step 404).Usually, more receive paths are needed for requested services requiringhigh data rates. For example, in a remote unit, such as remote unit 100,that has two antennas, the predetermined number of enabled receive pathsfor data services is two and the predetermined number of enabled receivepaths for voice services is one. In one implementation, new requestedservices, i.e., those available after the remote unit has beenprogrammed, are characterized as being either voice or data type and areassigned a predetermined number receive paths according to theircharacterization. For example, a new data service is assigned apredetermined number of two receive paths and a new voice service isassigned a predetermined number of one receive path. Optionally, thenumber of predetermined receive paths to be enabled for a givenrequested service can be changed.

FIG. 5 shows a flow diagram of a method for conserving power in aspatial processing remote unit, such as remote unit 100, in accordancewith one embodiment of the invention. As shown, the remote unitdetermines a performance level for the remote unit (step 502). In oneembodiment, the remote unit determines a performance level from time totime. In other embodiments, determinations are continuously derived,periodically derived, derived with a variable duty cycle, or derivedusing any combination of these methods. The remote unit then enables ordisables receive paths in response to the determined performance level.In one embodiment, the remote unit estimates by measuring certainindicia of performance, examples of which include but are not limited toBER, FER, SINR, SNR, and RSSI. The remote unit selectively enables anadditional receive path when the estimated performance level satisfies afirst set of conditions (step 504). As an example, the first set ofconditions can include a condition that BER exceeds a threshold BER anda condition that another receive path is available for enabling. Theremote unit selectively disables an enabled receive path when theestimated performance level satisfies a second set of conditions (step506). As an example, the second set of conditions can include acondition that BER is less than or equal to the threshold BER and acondition that more than one receive path is currently enabled.

FIG. 6 is a flow diagram for determining, during spatial processingoperations, when to enable an additional receive path (i.e., step 504 ofFIG. 5) and when to disable an enabled receive path (i.e., step 506 ofFIG. 5). As show in FIG. 6, a remote unit monitors and determines if theaverage FER is less than or equal to a first threshold (decision step602). If the average FER is not, then the remote unit determines whetherall receive paths are enabled (decision step 604). If not all receivepaths are enabled, then the remote unit enables an additional receivepath (step 606). If the average FER is less than or equal to the firstthreshold, then the remote unit determines whether there is more thanone receive path enabled (step 608). If there is, then the remote unitdisables an enabled receive path (step 610). Using logic implementingthe flow shown in FIG. 6, the remote unit 100 in one embodimentdynamically and selectively enables and disables receive paths duringspatial processing operations. In one implementation, the remote unit100 enables and disables one receive path at a time. Alternatively, anyindividual or combination of indicia of performance, such as SINR, SNR,RSSI, or BER can be used in place of FER. Optionally, the remote unit100 also measures the signal quality of each diversity branch of areceived signal and disables the receive path with the diversity branchhaving the lowest signal quality.

FIG. 7 is another flow diagram for determining, during spatialprocessing operations, when to enable an additional receive path (i.e.,step 504 of FIG. 5) and when to disable an enabled receive path (i.e.,step 506 of FIG. 5). As shown in FIG. 7, a remote unit determines if theaverage FER is less than or equal to a first threshold (decision step702). If the average FER is not, then the remote unit determines if theaverage FER is less than or equal to a second threshold that is greaterthan the first threshold (decision step 704). If the average FER is not,then the remote unit determines whether all receive paths are enabled(decision step 706). If they are not all enabled, then the remote unitenables an additional receive path (step 708). Otherwise, the remoteunit does not enable an additional receive path. If the average FER isless than or equal to a first threshold, then the remote unit determineswhether more than one receive path are currently enabled (decision step710). If there are more than one enabled receive path, then the remoteunit disables an enabled receive path (step 712). Optionally, the remoteunit also measures the quality of each version of a received signal anddisables the receive path(s) with the lowest quality version.

Methods for Adjusting Feedback

In addition to having an onboard spatial processing unit for improvingperformance and a power conservation unit for conserving power duringspatial processing operations, a remote unit in accordance with theinvention also includes a feedback adjustment unit for allowing theremote unit to benefit from any performance level increase that theonboard spatial processing unit provides. As discussed above, thefeedback adjustment unit 118 includes feedback adjustment logic foradjusting feedback that the remote unit transmits to a base station.Some illustrative feedback adjustment methods for increasing performancelevel are described below.

FIG. 8 shows a flow diagram of a method 800, in accordance with oneembodiment of the invention, for adjusting feedback to allow a remoteunit to benefit from spatial processing gains. As shown, during spatialprocessing operations, the remote unit periodically exits the spatialprocessing mode and temporarily operates in a non-spatial processingmode (step 802). The remote unit determines its performance level whilein the non-spatial processing mode (step 804). The remote unit uses thedetermined performance level to adjust feedback so that the feedbackrepresents the measured level of performance for the non-spatialprocessing mode (step 806). In one implementation, the remote unitoperates in a non-spatial processing mode by disabling all but onereceive path. Alternatively, the remote unit operates in a non-spatialprocessing mode by disabling one or both of the spatial processing unitand all but one receive path.

FIG. 9 shows a flow diagram of a method 900, in accordance with oneembodiment of the invention, for adjusting feedback to allow a remoteunit to benefit from spatial processing gains. The remote unitdetermines a performance gain that the spatial processing unit provides(step 902). The determined performance gain in one embodiment is theaverage performance gain during a given period of spatial processingoperations. Alternatively, another method of determining performancegain can be used. The remote unit determines a performance level whileoperating in a spatial processing mode (step 904). The remote unitaccounts for the determined gain from the determined performance levelto derive an adjusted performance level associated with non-spatialprocessing operations (step 906). The remote unit uses the adjustedperformance level to adjust feedback so that the feedback represents alevel of performance associated with the non-spatial processing mode(step 908).

FIG. 10 shows a flow diagram of a method 1000, in accordance withanother embodiment of the invention, for adjusting feedback to allow aremote unit to benefit from spatial processing gains. The remote unitdetermines the type of service being requested (step 1002). The types ofservice are similar to those discussed above. The remote unit adjustsfeedback by a predetermined amount that corresponds to the type ofrequested service (step 1004). In one implementation, the predeterminedamount is zero for voice services and, for data services, is an amountcorresponding to the average spatial processing gain. Alternatively, thepredetermined amount is proportional to the data transfer rate tosatisfactorily support the type of requested service. That is, arequested service that should use a high data transfer rate results in afeedback to the base station that does not reflect the gain that theonboard spatial processing unit provides. In this last case, thepredetermined amount is limited so that the feedback does not indicate aperformance level that is below a particular wireless system's operatingparameters, system architecture, or standard. In response to theadjusted feedback, a base station receiving the feedback does not lowertransmit power when the remote unit's performance level improves.Consequently, the remote unit benefits from performance gained from theonboard spatial processing unit.

It will be appreciated form the foregoing that the invention, includingthe described methods and logic, can be implemented in digitalelectronic circuitry, or in computer hardware, firmware, software, or incombinations of them. In one embodiment, the invention is implemented atleast in part in digital electronic circuitry, including but not limitedto application specific integrated circuits (“ASIC”). Similarly, inanother embodiment, the inventions is implemented at least in part indigital electronic circuitry, including but not limited tofield-programmable gated arrays (“FPGA”). Apparatus of the invention canbe implemented in a computer program product tangibly embodied in amachine-readable storage device for execution by a programmableprocessor; and method steps of the invention can be performed by aprogrammable processor executing a program of instructions to performfunctions of the invention by operating on input data and generatingoutput. The invention can be implemented advantageously in one or morecomputer programs that are executable on a programmable system includingat least one programmable processor coupled to receive data andinstructions from, and to transmit data and instructions to, a datastorage system, at least one input device, and at least one outputdevice. Each computer program can be implemented in a high-levelprocedural or object-oriented programming language, or in assembly ormachine language if desired; and in any case, the language can be acompiled or interpreted language. Suitable processors include, by way ofexample, both general and special purpose microprocessors.

The invention has been described in terms of particular embodiments.Other embodiments are within the scope of the following claims. Forexample, steps of the invention can be performed in a different orderand still achieve desirable results.

1. A remote unit, comprising: a spatial processing unit to couple to aplurality of antennas, the spatial processing unit having a logic unitto perform spatial processing of signals received by the plurality ofantennas, the spatial processing to include spatial combining ofselectively weighted versions of signals received on the antennas; aplurality of receive paths, each receive path to couple between one ofthe plurality of antennas and the spatial processing unit, wherein thereceive path includes components for processing received signals; logicto determine a number of the plurality of the receive paths to enablefor spatial processing; and a controller to enable and disable one ormore of the plurality of receive paths depending on the determinednumber.
 2. The remote unit of claim 1, further comprising: means forenabling and disabling the spatial processing unit, causing the remoteunit to operate in a spatial processing mode and a non spatialprocessing mode, respectively.
 3. The remote unit of claim 1, whereinantennas of at least a subset of the plurality of antennas havedifferent characteristics relative to one another.
 4. The remote unit ofclaim 3, wherein the different antenna characteristics is caused byantennas in the subset being physically separated relative to eachother.
 5. The remote unit of claim 3, wherein the different antennacharacteristics is caused by each of the subset having differentorientations.
 6. The remote unit of claim 5, wherein the differentantenna characteristics is caused by each of the subset havingsubstantially orthogonal orientations relative to one another.
 7. Theremote unit of claim 3, wherein the different antenna characteristics iscaused by each of the subset having a different material composition. 8.The remote unit of claim 3, wherein the different antennacharacteristics is caused by each of the subset having different shapes.9. The remote unit of claim 1, wherein logic for determining the numberof the plurality of receive paths to enable includes: logic forestimating a performance level of the remote unit; and logic fordetermining the number of receive paths to enable based on the estimatedperformance level.
 10. The remote unit of claim 9, wherein: the remoteunit supports one or more types of requested services; and the logic fordetermining the number of receive paths is further based on the type ofrequested service.
 11. The remote unit of claim 10, wherein the types ofrequested service includes voice service and data service.
 12. Theremote unit of claim 10, wherein the logic for determining the number ofreceive paths to enable includes: logic specifying a first predeterminednumber of receive paths to enable when the type of service is associatedwith a first data rate; and logic specifying a second predeterminednumber of receive paths to enable when the type of service is associatedwith a second data rate that is lower than the first data rate.
 13. Theremote unit of claim 9, wherein: the controller from time to timeenables all receive paths; the logic for estimating performance levelincludes logic for measuring performance when all the receive paths areenabled; and the logic for determining the number of receive paths toenable includes logic for evaluating whether power conserved bydisabling an enabled receive path warrants a loss in performance levelfrom disabling the enabled receive path.
 14. The remote unit of claim 9,wherein: the logic for determining the number of receive paths to enableincludes logic for determining whether the estimated performance levelsatisfies a first and second distinct set of conditions; and thecontroller enables an additional receive path when the estimatedperformance level satisfies the first set of conditions and disables anenabled received path when the estimated performance level satisfies thesecond set of conditions.
 15. The remote unit of claim 14, wherein: thefirst set of conditions include a condition that the estimatedperformance level is less than a first threshold performance level; andthe second set of conditions include a condition that the estimatedperformance level is not less than the first threshold performancelevel.
 16. The remote unit of claim 15, wherein: the first set ofconditions further include a condition that the estimated performancelevel is less than a second threshold performance level that is lessthan the first threshold performance level.
 17. The remote unit of claim9, wherein logic for estimating performance levels includes logic forcalculating metrics of signal quality.
 18. The remote unit of claim 9,wherein logic for estimating performance levels includes logic forcalculating bit error rate.
 19. The remote unit of claim 9, whereinlogic for estimating performance levels includes logic for calculatingframe error rate.
 20. The remote unit of claim 9, wherein logic forestimating performance levels includes logic for calculating receivedsignal strength.
 21. The remote unit of claim 1, wherein enabling areceive path includes providing power to the receive path, and whereindisabling a receive path includes not providing power to the receivepath.
 22. A remote unit, comprising: a spatial processing unit includinga processor and receive paths to couple to a plurality of antennashaving diversity, the spatial processing unit to combine weightedversions of a signal received on the antennas; a performance estimationunit to estimate performance of the remote unit, including periodicallycausing the remote unit to operate in a non-spatial processing mode andmeasuring a performance level of the remote unit while the remote unitis operating in a non-spatial processing mode; and a power conservationunit to selectively enable and disable at least a portion of the spatialprocessing unit based on the performance estimated by the performanceestimation unit.
 23. The remote unit of claim 22, wherein antennas of atleast a subset of the plurality of antennas have differentcharacteristics relative to one another.
 24. The remote unit of claim23, wherein the different antenna characteristics is caused by each ofthe subset having different orientations.
 25. The remote unit of claim23, wherein the different antenna characteristics is caused by each ofthe subset having a different material composition.
 26. The remote unitof claim 23, wherein the different antenna characteristics is caused byeach of the subset having different shapes.
 27. The remote unit of claim22, wherein the estimation unit to estimate performance includes theestimation unit to calculate metrics of signal quality.
 28. The remoteunit of claim 22, wherein the estimation unit to estimate performanceincludes the estimation unit to calculate frame error rate.
 29. Theremote unit of claim 22, wherein the estimation unit to estimateperformance includes the estimation unit to calculate bit error rate.30. The remote unit of claim 22, wherein the estimation unit to estimateperformance includes the estimation unit to measure received signalstrength.
 31. The remote unit of claim 22, wherein the powerconservation unit: determines whether the estimated performance levelsatisfies a first set of conditions and whether the estimatedperformance level satisfies a second set of conditions; and selectivelyenables an additional receive path when the estimated level ofperformance satisfies the first set of conditions and disables anenabled receive path when the estimated performance level satisfies thesecond set of conditions.
 32. The remote unit of claim 22, wherein: thefirst set of conditions include a condition that the estimatedperformance level is less than a first threshold performance level; andthe second set of conditions include a condition that the estimatedperformance level is not less than the first threshold performancelevel.